Big fish, small fish: Two New Ultra-Faint Satellites of the Milky Way

V. Belokurov, M. G. Walker, N. W. Evans, G. Gilmore, M. J. Irwin, D. Just, S. Koposov, M. Mateo, E. Olszewski, L. Watkins, L. Wyrzykowski

Published 2010-02-02Version 1

We report the discovery of two new Milky Way satellites in the neighboring constellations of Pisces and Pegasus identified in data from the Sloan Digital Sky Survey. Pisces II, an ultra-faint dwarf galaxy lies at the distance of ~180 kpc, some 15 degrees away from the recently detected Pisces I. Segue 3, an ultra-faint star cluster lies at the distance of 16 kpc. We use deep follow-up imaging obtained with the 4-m Mayall telescope at Kitt Peak National Observatory to derive their structural parameters. Pisces II has a half-light radius of ~60 pc, while Segue 3 is twenty times smaller at only 3pc.